The present invention relates to a direct positive silver halide photographic material, particularly to one having sufficient color reproduction quality to be advantageously used for color copying purposes.
In forming color photographic image by the subtractive process, yellow, magenta and cyan couplers are commonly used. The spectral absorptions of the resulting dye images are such that the magenta dye image has an unwanted absorption at 400-500 nm and 600-700 nm in addition to the main absorption, and the cyan dye image has such an unwanted absorption at 400-600 nm. These unwanted absorption cause color contamination which reduces the saturation of color images. Color photographs with reduced saturation do not have high commercial value, particularly in the case of reproducing graphic arts. In order to solve this problem, masking techniques such as by the use of colored couplers has heretofore been employed to compensate for unwanted absorptions in negative working light-sensitive materials. However, colored couplers are not suitable for use in positive working light-sensitive materials such as reversal materials and color papers since they produce increased minimum densities.
The use of compounds that are capable of reacting with the oxidation product of developing agents to release diffusible development restrainers or precursors thereof (such compounds are hereinafter referred to as "DIR compounds") is known as a technique for inhibiting the formation of colors in layers other than the one of interest which corresponds to the unwanted absorption.
Various versions of this technique are disclosed in U.S. Pat. No. 4,477,563, etc. However, if such DIR compounds are used in internal latent image forming direct positive light-sensitive materials, the released development restrainers are not sufficiently effective to inhibit the formation of colors in other layers by a satisfactory degree.
It is also known to incorporate compounds (DSR compounds) that are capable of reacting with the oxidation product of developing agents to release compounds capable of scavenging said oxidation product or precursors of such compounds, so that the layer containing such DSR compounds can be developed while a development restrainer acts on other layers. A problem also occurs when DSR compounds are used in internal latent image forming direct positive light-sensitive materials. In order to insure that the layer containing such DSR compounds can be developed without causing unwanted development of other layers, the DSR compounds have to be used in increased amounts but then there occurs not only a change in image color (as indicated by .lambda.s in FIG. 1) but also deterioration in the pot life of coating solutions (i.e., the stability of coating solutions after preparation, which is hereunder referred to simply as "digestion stability").
Therefore, a method has been desired that can be applied to internal latent image forming direct positive light-sensitive materials and by which the occurrence of color development in layers other than the one being developed can be restrained as a function of color formation in the latter without causing any change in image color or reduction in the digestion stability of coating solutions.